The XI International Youth Scientific School "The Coherent Optics and Optical Spectroscopy"
Formation dynamics of the radial-angular structure of the Rydberg wave-packet in a resonant microwave field.
P. A. Volkov,
M. A. Efremov,
M. V. Fedorov General Physics Institute named after A. M. Prokhorov, Russian Academy of Sciences
Abstract:
We discuss a very interesting experiment by H. Maeda, T. F. Gallagher, PRL 92, 133004 (2004), in which Li Rydberg atoms were exposed to an action of a resonant microwave filed (switched-on at
$t=0$). Then, in a varying time
$t_0$, the atoms were ionized by a strong sub-picosecond Half-Cycle Pulse. The probability of ionization
$w_i$ was measured in its dependence on
$t_0$ and the function
$w_i(t_0)$ was found to be oscillating with the classical Rydberg-atom Kepler period. The original author's explanation of this effect was based on the assumption that the resonant microwave field provided formation of a localized Rydberg wave packet moving along the classical Kepler trajectory and responsible for the observed periodical dependence of
$w_i(t_0)$. We suggest here an alternative interpretation of this result. By solving exactly the initial-value problem for a Rydberg atom in a microwave field we find that such a field does not provide any radial localization of a wave packet. On the other hand, it provides a rather efficient repopulation of the resonant Rydberg levels with high values of the angular momentum quantum number
$l$. Migration of population to high-
$l$ states is shown to cause a modulation of both angular and radial motion of a Rydberg electron. Such a periodical modulation of the electron motion is believed to provide a proper explanation of the experimental results by Maeda and Gallagher.
UDC:
539.182+539.184
Received: 03.02.2006